In those areas of the country subject to earthquakes, hurricanes, tornadoes, floods, or tidal action which impose upward forces on building structures, it has become standard practice to tie the structure to the concrete foundation.
The oldest and probably still the most common practice is to set anchor bolts threaded at their upper end in the foundation. When the concrete has hardened, holes are drilled in the wood mudsill and the mudsill is placed on the foundation with the anchor bolts extending through the holes. A washer and nut are placed on the anchor bolt and the bolt tightened down to hold the mudsill to the foundation.
Anchor bolts are sold in basically four different configurations; viz. J-bolt, L-bolt, hex head bolt and threaded rod with two nuts and washer.
The early construction practice was to simply toe nail the studs to the wood mudsill. It was soon learned, however, that in too many instances after an earthquake or hurricane, that the mudsill stayed anchored to the foundation, but the toe nailed studs were unable to hold the frame of the house to the mudsill. Several types of metal connectors followed which connected the studs to the anchor bolt, culminating in the holdown disclosed in U.S. Pat. No. 4,665,672 granted May 19, 1987 to Alfred D. Commins, Tyrell T. Gilb, and Karen W. Colonias.
With increased loads being transferred to the foundation anchor bolt through holdowns connected to the framing studs, it became apparent that greater attention must be paid to the connection of the anchor bolt in the foundation.
Anchor bolts with end protrusions such as the J-bolt and L-bolt which have greater anchorage in the foundation than straight bolts, can only achieve the increased load anchorage if the end protrusions are located inwardly from the edge of the concrete. If for example, the end protrusion of the anchor bolt comes too close to the edge of the foundation, bursting of the side of the foundation can occur at less than design loads. Further, an anchor bolt which is very close to the edge of the concrete or even protrudes through the concrete is more subject to corrosion. There is presently no means, however, to determine the orientation of the bolt after the concrete has been poured and hardened. Inspection to determine proper orientation of prior art bolts is impossible.
Another problem with the prior art anchor bolts is that the portion of the bolt which extends vertically, whether it is a straight bolt, a J-bolt, or an L-bolt or any other configuration, contributes limited pull out resistance. Only the friction between the sides of the bolt and the concrete resists pull out in the vertical portion.